MySpace still top dog, but Facebook gaining fast

News Corp.’s (NWS) MySpace is still king of the hill in social networking, but rival Facebook was climbing fast in September, according to the latest numbers released today from Nielsen Online. MySpace registered 58.6 million unique visitors in September, up a respectable 24 percent from a year before. But Facebook turned on the turbo jets: it registered 18 million unique visitors, up 133 percent.

Nielsen did not offer a reason for Facebook’s rapid growth. But Facebook has garnered attention over the past several months because of its unorthodox strategy of freely allowing outside developers to write software for its social networking platform. By writing programs for the Facebook platform, developers have been able to quickly amass users as they recommend new programs to their friends.

There have been rumors that Facebook is talking to Microsoft (MSFT), Google (GOOG), Yahoo (YHOO) and others about taking an equity stake in the company.

Facebook’s relatively open platform stands in contrast to MySpace. Until recently, MySpace was known to occasionally block software developers from promoting their wares on the site, particularly if the developers were making money from advertising. But in the face of mounting competition from Facebook, MySpace appears to be changing its tune. News Corp. executives say MySpace will soon follow Facebook in providing an open developer platform.

Nielsen also released numbers that show Google’s Blogger was still the most popular blogging platform in September, with 29.6 million unique visitors, up 50 percent from a year earlier. But the true growth story in blogs appears to be WordPress. WordPress’s unique audience jumped 290 percent year-over-year to 10.4 million, probably because the tool became available as a Blogger-like service that’s freely available. (Big Tech is published on WordPress.)

Table 1: Top 10 Social Networking Sites for September 2007 (U.S., Home and Work)